Patent Literature 1 proposes a technique of using a trochoid propulsion system to move a legless-chair type vehicle omni-directionally on the floor, the vehicle including eight casters exposed downward and a pair of antislip rear wheels. This system includes the eight casters uniformly arranged around a pivot of a turning cylinder and allows a tie rod engaged with each of the eight casters to steer the rotating directions of the eight casters. More specifically, the tie rod corresponding to each caster is configured to be integrally rotatable with a central base, and in the state where the central base and the pivot coincide with each other in their positions, the cylinder simply turns and the vehicle is in a stopped state. On the other hand, when a steering operation is performed to decenter the position of the central base from the pivot on the horizontal plane, the vehicle travels in a translational mode in the decentering direction while letting the casters turn. Similarly, Non-Patent Literature 1 also discloses an omni-directional drive system including a plurality of passive wheels equipped with steering mechanism that are arranged circumferentially around a vertical rotative driving axle.
Patent Literatures 2, 3 and Non-Patent Literatures 2, 3 disclose a propulsion system having a propulsion principle similar to that of a helicopter, a cycloidal or a propeller and having an axisymmetric omni-directional property, and especially disclose a system to continuously change the translational velocity. Non Patent Literature 4 describes a propulsion, system based on a meandering motion equipped with a system to adjust the camber angle.